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Statement of the Problem Recent interest in shaded zirconia has raised questions about the relative stability of the tetragonal phase after colorant oxide additions. Purpose The purpose of this in vitro study was to evaluate the effects of fatigue cycling on the stability of a commercially available dental zirconia (Procera) in both unshaded and shaded compositions by measuring the change in biaxial flexural strength (BFS) after 500 000 cycles at 80-N loads and in phase composition as detected by x-ray diffraction (XRD). Material and Methods Partially stabilized zirconia disks (NobelProcera) were fabricated in unshaded and shaded forms (12 mm diameter × 0.8 mm thick). Specimens were analyzed by energy-dispersive x-ray spectroscopy (EDS) and by wavelength-dispersive x-ray spectroscopy (WDS) for oxide compositions which indicated the presence of small amounts of Fe-O (0.13 ±0.10 wt %) in the shaded specimens. XRD focused on the tetragonal (T) and monoclinic (M) peaks in the 20 to 40 degrees 2θ range. The disks were polished on 1 side, cyclically loaded (80N, 500 000 cycles, custom 4-station fatigue test machine), and tested for residual BFS after cycling. Unshaded (U) and shaded groups (S) were compared before (U1, S1) and after (U2, S2) load cycling with XRD and residual BFS. Results Residual BFS (MPa) for specimens before (U1=856 ±99 versus S1= 842 ±40) and after fatigue (U2=772 ±65 versus S2= 718 ±68) were statistically different (U1 versus U2; S1 versus S2; U2 versus S2, P

We determine the three-dimensional equilibrium shapes of particles with a purely dilatational misfit in an elastically anisotropic medium with cubic symmetry. We have identified a succession of cuboidal shapes with four-fold rotational symmetry that minimize the total energy of the system. In the process of determining these equilibrium morphologies, we have also developed a computationally efficient approach to determine the equilibrium shape which is many orders of magnitude faster than a standard implementation of Newton's method. For small elastic stress a (100) cross-section of the three-dimensional equilibrium shape agrees well with the two-dimensional calculation. However, for larger values of the elastic stress, the agreement is not as good. Elastic-stress-induced configurational forces are identified as the reason for the non-spherical equilibrium shapes.

TFTR has begun its campaign to study deuterium-tritium fusion under reactor-like conditions. Variable amounts of deuterium and tritium neutral beam power have been used to maximize fusion power, study alpha heating, investigate alpha particle confinement, and search for alpha driven plasma instabilities. Additional areas of study include energy and particle transport and confinement, ICRF heating schemes for DT plasmas, tritium retention, and fusion in high βp plasmas. The majority of this work is done in the TFTR supershot confinement regime. To obtain supershots, extensive limiter conditioning using helium fueled ohmic discharges and lithium pellet injection into ohmic and neutral beam heated plasmas is performed, resulting in a low recycling limiter. The relationship between recycling and core plasma confinement has been studied by using helium, deuterium and high-Z gas puffs to simulate high recycling limiter conditions. These studies show that confinement in TFTR supershots is very sensitive to the influx of neutral particles at the plasma edge.

Both global and thermal energy confinement improve in high-temperature supershot plasmas in the Tokamak Fusion Test Reactor (TFTR) when deuterium beam heating is partially or wholly replaced by tritium beam heating. For the same heating power, the tritium-rich plasmas obtain up to 22% higher total energy, 30% higher thermal ion energy, and 20-25% higher central ion temperature. Kinetic analysis of the temperature and density profiles indicates a favorable isotopic scaling of ion heat transport and electron particle transport, with τEi(a/2) ∝ A0.7-0.8 and τpe(a) ∝ A0.8.

The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approximately}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning; possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the P{sub FUS} {approximately}6 MW level. Instability in the TAE mode frequency range has been observed at P{sub FUS} > 7 MW and its effect on performance is under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fullymore » explored.« less

We examine the equilibrium morphologies of precipitates with either a tetragonal or purely dilatational misfit in an elastically anisotropic medium with cubic symmetry under conditions of plane strain. We find that particles with a dilatational misfit are nearly spherical at small sizes, take on four-fold symmetric shapes at intermediate sizes and then undergo a supercritical symmetry-breaking bifurcation to two-fold symmetric shapes aligned along the elastically soft directions of the crystal. A tetragonal misfit breaks this four-fold to two-fold supercritical bifurcation when the direction of the tetragonality is coincident with one of the elastically soft directions of the crystal. Such a tetragonal misfit can lead to two-fold equilibrium particle shapes which are local energy minima, or metastable, and in some cases have large negative interfacial curvatures. When the tetragonality is not in an elastically soft direction, the supercritical bifurcation is not broken and the particles can take on unusual diamond-like or S-shaped morphologies.

Three isoenzyme forms (designated A, B, and C) of O-acetylserine sulfhydrylase were purified from Datura innoxia suspension cultures. Isoenzyme A is the most abundant form, comprising 45-60% of the total activity. Isoenzymes C and B comprise 35-40% and 10-20% of the activity, respectively. The specific activities of the purified isoenzymes are similar (870-893 mumol of cysteine/min/mg of protein). Molecular masses for isoenzymes A, B, and C, estimated by analytical size exclusion high performance liquid chromatography, are 63, 86, and 63 kDa, respectively. Isoenzymes A and B are homodimers; isoenzyme C is a heterodimer. Spectral analysis indicates that these isoenzymes possess a pyridoxal 5'-phosphate cofactor that binds the O-acetylserine substrate. Binding is reversible by addition of the sulfide substrate. The O-acetylserine sulfhydrylase isoenzymes are active over a broad temperature range, with maximum activity between 42 and 58 degrees C. They are active only between pH 7 and 8, with optimal activity at pH 7.6. Kinetic analysis indicates these enzymes are allosterically regulated and exhibit positive cooperativity with respect to both substrates. They are inhibited by sulfide concentrations above 200 microM. The kinetic analysis together with the physical and spectrophotometric characteristics indicate that the O-acetylserine sulfhydrylase enzymes have two active sites.

Summary Objective This article describes the experience of four acupuncturists in terms of what it meant for them to be a practitioner in a recently completed sham-controlled acupuncture randomized control trial (RCT) with a standardized protocol. Design At the completion of the RCT for women with ovarian dysfunction, study acupuncturists (2 male MD/acupuncturists and 2 female professional acupuncturists) were queried about their perceptions of participating in the RCT using both written responses to 5 open-ended questions and a focus group interview. Data was analyzed to categorize responses and identify themes. Setting Virginia, USA. Results The acupuncturists' experience of participating in a RCT was generally very positive, including: usual practitioner/participant relationships, collegial sharing, and increased patient volume and diversity. There was angst expressed about the unknown RCT results. While there were concerns about standardizing the acupuncture session ("dilutes the power of acupuncture therapeutics"), the acupuncturists' were supportive of the pre-established protocol. The acupuncturists overall did not have concerns with a sham intervention arm because the sham recipients did not know their treatment arm and felt as satisfied with study participation as the true acupuncture recipients. Conclusions Despite initial misgivings about both a standardized protocol and a sham arm, all practitioners discovered positive aspects of being a study acupuncturist. The analysis highlights the need for communication before, during and after a clinical trial between the study investigators and the intervention practitioners. As stake holders in the perception of CAM therapies with the public and with conventional medicine practitioners, it would benefit future research on CAM to similarly assess experiences of being a CAM study practitioner in order to enhance provider recruitment and reduce provider drop-out.

The problem of Bayesian estimation of a continuous time stochastic ‘signal’ process, on which the observation process depends linearly, is discussed. It is noted that the situation treated by Ammann (Stochastic Processes and their Applications, 1985) is a special case. Considerations involved in the generalization of his Laplace transform functional approach are described.

In this article, a new method for performance evaluation of turbo-like codes is presented. This is based on estimating the probability density function (pdf) of the bit log-likelihood-ratio (LLR) using higher order statistics. We do not restrict ourselves to any specific model for the pdf and try to estimate it directly using a cumulant matching method. Numerical results show a close agreement between the proposed method and simulations. The complexity of this method is similar to the Monte-Carlo simulation with the advantage of providing similar accuracy using significantly fewer samples.

Transient heat transfer, fluid flow and phase change in a weldpool with a deformed free surface are modelled using a two-dimensional coordinate transformation. The theoretical approach makes it possible to accurately model high Marangoni number flows even when the free surface is not horizontal. The method is used to examine the role of surface deformation and surface tension forces in controlling weld penetration during cathode spot welding of steel and aluminum. The calculated flow fields, temperature distributions and weldpool shapes are consistent with experimental findings, and are in reasonable agreement with previously published modelling efforts.

Theoretical modelling and experimentation are used to analyze horizontal solidification of a double-diffusive, binary liquid in a confined rectangular cavity. For solutions which segregate the lighter component into the liquid, the composition and temperature gradients produced upon solidification lead to the onset of vertical counterbuoyant flow along the growing crystals. The counterflow progressively transforms the initially homogeneous liquid into a density-stratified fluid layer characterized by pronounced vertical gradients in solute concentration. The theoretical representation describes the coupling between the solidification and development of density stratification in the liquid in the interior of the cavity. The computed results and experimental observations indicate that for moderate horizontal temperature differences, the vertical stratification can effectively damp convection in the stratified portion of the bulk liquid. Increasing the temperature difference or lateral heat flux across the enclosure sufficiently, initiates formation of a series of horizontal double-diffusive convection layers. The nature of the fluid motion in the bulk is seen to have significant influence on solute redistribution and heat transfer, both at the growth interface and in the interior of the enclosure. The computed flow patterns, solid-liquid interface shapes, and rates of growth of the stratified region compare well with those observed experimentally for directionally-solidified solutions of sodium carbonate and water. The calculated and observed heights of the horizontal convection cells correlate well with theoretical predictions. Order-of-magnitude analysis is used to explore the theoretical limits of stability of the growing layer under the roof with respect to remixing with the underlying ‘bulk’ liquid.

Recently there has been a growing interest in the problems of inference for stochastic processes when the underlying distribution is not specified in terms of a parametric family. Godambe's (1985) approach is here employed to obtain estimates for random signals for a continuous semimartingale model. The method, which avoids specification of the underlying distribution, leads to estimation for nonconjugate prior situations which is computationally attractive as well as optimal in a restricted sense. A number of techniques in the recent literature are special cases.

This paper extends a result of Godambe's theory of parametric estimation for discrete-time stochastic processes to the continuous-time case. Let P ={P} be a family of probability measures such that (Ω, F, P) is complete, (Ft, t≧0) is a standard filtration, and X = (Xt Ft, t ≧ 0) is a semimartingale for every P ∈ P. For a parameter θ (Ρ), suppose Xt = Vt,θ + Ht,θ where the Vθ process is predictable and locally of bounded variation and the Hθ process is a local martingale. Consider estimating equations for θ of the form process is predictable. Under regularity conditions, an optimal form for α θ in the sense of Godambe (1960) is determined. When Vt,θ is linear in θ the optimal , corresponds to certain maximum likelihood or least squares estimates derived previously in special cases. Asymptotic properties of , are discussed.

A result of Godambe [1] on optimal combination of estimating functions for discrete time stochastic processes is extended to discrete time state space models and to continuous time counting process models. The extensions so obtained may be applicable in a wider context than the standard notions based upon the conditional mean. It is shown that a number of results in the literature are special cases. The theory is applied to obtain recursive estimates for continuous time counting processes. Optimal linear combination of estimating functions can shed light on the form of recursion satisfied by the usual filter, namely conditional expectation of the unobserved underlying process given the observation history.

Five sets of "close" samples (narrow and contiguous samples across a lithologic unit) from beds of high phosphate content of the Phosphoria formation in Idaho, Utah, and Wyoming were analyzed chemically for F and C02. The size of phosphate pellets was measured in thin sections of two sets of close samples. Frequency histograms and cumulative curves were plotted from these size measurements, but when compared with uranium concentration for each sample, no significant correlation between size and uranium concentration could be discovered. Analyses of these samples for P2P^t CaO, organic matter, and equivalent uranium were presented in a previous report. In two sets of samples a good correlation was found between equivalent uranium and each of the other components. The samples in these two sets have a uranium content that is relatively high (for the Phosphoria formation), and they show considerable variation in P® content. GEOLOGY ATJD MINERALOGY In the interest of economy, this report has been reproduced direct from copy as submitted to the Technical Information Service. Since nontechnical and nonessential prefatory material has been deleted, the first page of the report is page 5. AEC, Oak Ridge, Tenn.-W30816 FURTHER STUDIES OF THE DISTRIBUTION OF URANIUM IN RICH PHOSPHATE BEDS OF THE PHOSPHORIA FORMATION*

From abstract: "Five sets of 'close' samples were analyzed radiometrically for uranium, and chemically for P₂O₅, CaO, organic matter, and loss on ignition. A Rosiwal analysis was made of thin sections of one set of samples."